In recent years, efforts have been made to realize micro-machinery using technologies for manufacturing semiconductors. Mechanical electric elements, such as an actuator, are getting into the limelight. The use of such elements can realize small and high-precision machinery. Especially examined are applications of an actuator using piezoelectric elements for micro-positioning the head slider of a disk drive.
For instance, in a magnetic disk recording/reproducing device, the magnetic head for recording into or reproducing from a magnetic disk is mounted on the head slider and attached to the actuator arm. This actuator arm is rocked by a voice coil motor (hereinafter referred to as a “VCM”) so as to position the magnetic head in a specific track position on the magnetic disk for recording and reproduction. However, with improvements in recording density, a sufficient precision cannot be ensured by such conventional positioning which only use a VCM. For this reason, in addition to the positioning means using a VCM, a technique has been proposed for driving the head slider for high-speed and high-precision positioning with a micro-positioning means using piezoelectric elements. (“Switching to super-high TPI and piggy-back actuator”, IDEMA Japan News, International Disk Drive Equipment Material Association Japan, September, 1999, Vol. 32, pp 4–7).
As described above, actuators using piezoelectric elements are expected to find a wide range of applications. As disclosed in Japanese Patent Unexamined Publication No. H06-22448, many of the conventional piezoelectric elements are structured to be laminated by a green sheet lamination method or a thick film multilayer method. However, when the piezoelectric elements are produced by these manufacturing methods, the thickness of one layer of the piezoelectric elements measures several dozens micrometers. Thus, a drive voltage of at least 100V is necessary.
In contrast, Japanese Patent Unexamined Publication No. H08-88419 discloses a thin film laminated actuator which is small and capable of being driven at a low voltage and which has a large amount of displacement, and a method of manufacturing the actuator. The manufacturing method is described hereinafter. First, an electrode layer made of platinum (Pt), aluminum (Al), gold (Au), silver (Ag) or other materials, a piezoelectric layer made of a piezoelectric material including lead zirconium titanate (PZT), lead lanthanum zirconate titanate (PLZT), and an electrode layer made of the above-mentioned material are formed on a single-crystal substrate made of magnesium oxide (MgO), strontium titanate (SrTiO3), sapphire (Al2O3) or other materials. On these layers, an adhesive layer made of glass or silicon is formed to provide a piezoelectric member.
Thereafter, the two piezoelectric members are joined via the adhesive layers by an anode junction method. Then, one of the substrates is removed by grinding or another method. After the removal of one of the substrates, another adhesive layer is formed on the exposed electrode layer again. This adhesive layer and the adhesive layer of another piezoelectric member are joined again. By repeating these steps, a multilayered laminate is formed. Thereafter, a laminated actuator is produced by alternately leading the inner electrodes in this laminate from both sides.
Such a thin film laminated actuator features an inexpensive power supply circuit because the drive voltage is low. However, because external electrodes are formed from the two side faces of a laminate of multilayered piezoelectric members via insulating layers, the external electrodes must be formed for each laminate. This poses a problem in mass production. Additionally, because this actuator is structured so that displacement occurs in the direction perpendicular to the surface of the substrate, the shape of the actuator is not suitable as a micro-actuator for the head slider of a disk drive, for example.